B-cell lymphoma-2 phosphorylation at Ser70 site-related autophagy mediates puerarin-inhibited the apoptosis of MC3T3-E1 cells during osteoblastogenesis.

Objective: To explore the relationship between autophagy and apoptosis regulated by puerarin during osteoblastogenesis.

Methods: In this study, the effects of puerarin on the autophagic activity and apoptosis level of osteoblast precursors (MC3T3-E1 cells) was observed. Subsequently, the roles of puerarin on B-cell lymphoma-2 (Bcl-2) phosphorylation at different sites in osteoblast precursors were observed. The effect of puerarin on the interaction between Bcl-2 and autophagy regulatory molecule or pro-apoptotic molecule was also investigated using Co-immunoprecipitation assays. In addition, the effect of puerarin on mitochondrial membrane potential of osteoblast precursors was also identified by mitochondrial membrane potential fluorescence probe assays.

Results: Our results showed that puerarin can promote the autophagic activity and apoptosis level of MC3T3-E1 cells. In addition, puerarin promoted Bcl-2 phosphorylation at Ser70 site, and the dissociation of Bcl-2-Beclin1 complex. Moreover, puerarin could enhance the binding of Bcl-2-Bcl-2-Associated X (Bax) complex in MC3T3-E1 cells. Furthermore, puerarin increased the mitochondrial membrane potential of MC3T3-E1 cells.

Conclusions: Therefore, puerarin promotes Beclin1 into autophagy flux through Bcl-2 phosphorylation at Ser70, thereby enhancing autophagy of osteoblast precursors, which mediates its anti-apoptotic role during osteoblastogenesis. Furthermore, the dissociation of Bcl-2-Beclin1 complex is conducive to the binding of Bcl-2-Bax complex, which resists the apoptosis of osteoblast precursors viathe increased mitochondrial membrane potential.